Lower soil pH or wait?

9 years ago

We made major changes to our property on the coastal north shore of Boston this year bringing in about 300 yds of subsoil and 300 yds of improved loam to fill and plant over exposed ledge (granite) on a hillside of about .35 acres. We then planted perennials, deciduous and needle leaf trees, shrubs including rhodies, blueberry, and azalea, and some lawn in May and June. All the plantings have shredded bark mulch surrounding them.

The results of 2 UMass soil tests from different samples came back last week showing the same values. All macro and micro nutrients are in the range Optimum or Above Optimum except nitrogen which was 4 ppm.

My question is about the pH of 7.5, high for this region. I want to bring this down about 1 point most places and more than that for the acid lovers by adding sulfur but given all the newly added soil I'm not sure if the pH is stable or may be changing. The soil test showed sulfur content of 53 ppm. Any advice on whether I should add sulfur now or wait some months and get another test?

This post was edited by elfowl77 on Thu, Aug 21, 14 at 10:03

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Comments (8)

Kimmsr
9 years ago
The people at your local UMASS Cooperative Extension Service office would be better able to answer that question because it will vary depending on which plant you are working with.
Understand that changing the soils pH is going to take some months and is not something that will happen shortly.
mad_gallica (z5 Eastern NY)
9 years ago
The pH is fine for most plants. You may find some 'mysterious' failures, but I wouldn't worry about it. The lawn will be fine, and so will most of the perennials.

The acid lovers, of course, are a different matter. Whatever you do, you may lose them, but adding sulfur is a start. You'll want to do another test next spring just to see what is going on.

Do you know of any local places with lime in their name? There are around here, and Soil & Water tells me that the natural pH can be as high as 8 locally.
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If drainage is a problem, you can use sand if you create mounds for the plants using a great deal of sand. A little sand can actually make things worse from research I've seen, but if you use something like a third sand by volume, mixed with a third peat and a third soil and create the mounds with this it should work fine. If you make such a mix without building mounds you may create bath tubs that fill with water and drown roots. You can also grow them in pots mixing 50/50- sand to peat and put them half way into existing soil- or make a mix with ground pine bark that is aged for the purpose (this is harder to find but more often used in blueberry production). If you set up a drip system or water them consistently, blueberries grow very well this way, if you put them in big enough pots. 5 gallon pots would support mature plants pretty well. Is your soil clay? Do you know the texture of your soil? This is something that is not at all obvious and people often are confused about the texture of their soil. This is also where your county cooperative extension can provide better advice than you can get on-line- although there are simple tests using dishwater detergent to get a general reading on your soils composition. Drainage is easier, because you can figure out how long it takes to drain after heavy rains or dig a hole and fill it with water several times. Not sure of the exact procedure but it is an easy search for details.
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It helps to know something of the natural history of your area. For example, our soil, here in Madison, Wisconsin, was once a seabed, during a long period when much of North America was covered by saltwater. We have two layers of limestone, formed from the leftover seashells and diatoms that sank to the bottom when the creatures died. Our native soil has a pH around 7.6, and our garden is healthy and productive, with only compost added to help loosen up the clay. Our compost starts out with shredded maple tree leaves, and there is also yard waste added, but not very much nitrogen source. I suspect that there are thousands, if not tens of thousands of folks in the midwest gardening successfully in soil similar to ours. However, we also grow blueberries, and we are using agricultural sulfur to lower soil pH, down to the range: 4.5 - 6.5, essential for blueberry success. Its not that hard to lower soil pH, but you will need to learn how to measure soil pH, so you know where the soil is at, before and after applications of sulfur.
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If you're going to proceed without a good soil test (and sadly, the home kits don't really count), you should do your homework. I understand your desire to save some money! What do your neighbors say that their soil always needs? What is the conventional wisdom in your area? Where I live, for instance, the soil tends to be generally pretty good, but somewhat on the acidic side. Conventional wisdom (and my grandmother, and all of the other gardeners in the area) say that adding lime will be necessary where I live. In fact, when I don't do this, I get Blossom End Rot (a sign of calcium deficiency) on my tomatoes and peppers, and when I add some lime, it goes away. Does the conventional wisdom of your area say that the soil is always alkaline, and you'll need to lower the pH? If so, products to help you to do this will be available in your area, certainly at a garden store, and quite likely at the "big box" stores like Home Depot (though I might have a bit of trouble finding that stuff where I live, since we have the opposite problem here). If pH-lowering supplies aren't readily available in the local garden stores, I'd have additional doubts about what your home soil test told you. Adding organic matter is always a good step, even without a soil test. As people have said, lots of good organic matter will bring your soil back towards neutral, regardless of where is started, and it will also add lots of the nutrients your plants need to be happy and healthy. I believe it is possible to garden (and even to garden well) without a soil test, but you need to keep on your toes. People gardened for a good long time without access to soil tests, but the other side of that is that the successful folks knew how to read their soil and their plants to detect deficiencies.
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elfowl77
Original Author
9 years ago
Thanks for the tips. Our local soil is usually in range 6-7. All of this soil was brought in earlier this spring...not sure from where but probably nearby New England.

I realize it will take a long time for the sulfur to work, and not much will happen during the cold months, but was wondering if I should get the process underway now or wait until Spring to see if the 53 ppm S currently in the soil will acidify it.

I'll check with umass too.
Slimy_Okra
9 years ago
"wait until Spring to see if the 53 ppm S currently in the soil will acidify it. "

No, it won't. That sulfur is in the form of a neutral sulfate salt, probably calcium or magnesium sulfate. Sulfur has to be in the form of elemental sulfur or an acidic sulfate salt (iron sulfate, ammonium sulfate, aluminium sulfate) to have an acidifying effect, with elemental sulfur giving you the most bang for your buck.

Since 7.5 is close to the acceptable range, and because the surrounding soil is acidic, I would try to lower the pH using ammonium sulfate and organic sources of nitrogen. With elemental sulfur, there is always the risk of overshooting your target.
elfowl77
Original Author
9 years ago
OK, again thanks and sounds like good advice. I thought it might be useful to post a screenshot of the test results. Does anything stand out to you experts?
toxcrusadr
9 years ago
Is the soil just topsoil or is it some kind of garden mix with compost or manure mixed in? If it's a mix it may have had alkaline manure mixed in. In which case it will not stay up there permanently. Just a thought. I don't have much to add to what's been said already.
lazy_gardens
9 years ago
Also a factor ... how do the plants look?

If they are sending out now growth and in general looking "happy" I'd leave it and see what happens.

If they are not increasing in size, yellowing, dropping leaves and doing the unhappy plant stuff ... see about lowering the pH.
elfowl77
Original Author
9 years ago
It is a "planting soil" and is supposed to contain compost and I think it does given the test results including near 6% organic content. My inclination is to go slow and watch what's happening.

The plants are generally happy keeping in mind that everything (60 trees and similar number of shrubs plus hundreds of perennials) was just planted this spring. There's some transplant shock and we have lost a few trees and shrubs but overall they look pretty good. We have had a very dry (for NE) cool summer.

Surprising to me the blueberries all look great. Their leaves look good, starting to turn normal red. The azaleas are also mostly happy.

The perennials were looking nitrogen starved and i have now fertilized them. On the advice of an arborist I'm not adding any fertilizer this year to the trees as they settle in.

Lower soil pH or wait?

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Kimmsr

mad_gallica (z5 Eastern NY)

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Lower soil pH or wait?

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Kimmsr

mad_gallica (z5 Eastern NY)

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